   the the radius slope, or the slope of the tangent to that radius"
   [radius slope]
   {:pre [(every? number? [radius slope])]}
-  (/ radius (.sqrt js/Math (+ 1 (* slope slope)))))
+  (/ radius (.sqrt js/Math (+ 1 (square slope)))))
 
 
 (defn arc-x-distance

        intersect-y (/ (+ (* src-radius dest-y)
                          (* dest-radius src-y))
                       total-arc-radius)
        src-radius2 (* src-radius src-radius)
        src-center-intersect-dx (- intersect-x src-x)
        src-center-intersect-dx2 (* src-center-intersect-dx
                                    src-center-intersect-dx)
        src-center-intersect-dy (- intersect-y src-y)
        src-center-intersect-dy2 (* src-center-intersect-dy
                                    src-center-intersect-dy)
        src-center-intersect-dx2-dy2 (+ src-center-intersect-dx2
                                        src-center-intersect-dy2)
        ;; In the triangle formed by arc center, tangent point, and intersect,

         (map (fn [[node y]]
                [node (+ y delta)]))
         (into {}))))


(defn square [x]
  (* x x))


(defn check-alignment
